SMD, which is the abbreviation of Surface Mounted Device, is one of SMT (Surface Mount Technology) components. In a primary stage of production of an electronic circuit board, through hole assembly is carried out completely manually. After the first batch of automated machines have been launched, some simple pin elements can be placed thereby, however, complicated elements still need to be placed manually for wave soldering. Its assembly density is high, and an electronic product obtained has a small volume, the volume and weight of a surface mounted element are only about 1/10 of those of a traditional element mounted by insertion, so it has a light weight, high reliability, strong shock resistance, low soldering defect rate, and excellent high frequency characteristics, reduces electromagnetic and radio-frequency interference, is easy to achieve automation, has high production efficiency, reduces cost by up to 30% to 50%, and saves materials, energy, devices, manual labor, time, and so on.
A micro SMD is a standard thin product. An SMD chip has a surface with solder bumps. Steps of the production process of the micro SMD comprise fabrication of a standard wafer, re-passivation of the wafer, deposition of eutectic solder bumps on an I/O bonding pad, back grinding (only used for thin products), coating of a protective package, testing by a wafer selection platform, laser labeling, packing into a form of tape and reel, and final assembly on a PCB by using a standard surface mount technology (SMT). The micro SMD is a wafer-level chip scale package (WLCSP), which has the following features: a package size identical with a bare chip size; the smallest I/O pin; no need of underfill material; a wiring spacing of 0.5 mm; and no need of interposer between a chip and a PCB.
An SMD holder is configured to fix a chip to be packaged into a lamp bead. An SMD holder in the prior art is a hollow housing with one end opened and has sidewalls made from a nontransparent material. The bottom of the holder is sequentially divided into a first function area, an insulation area, and a second function area along a direction perpendicular to the sidewalls of the holder. The insulation area is made from a nontransparent material, and the first function area and the second function area adopt metal materials. Area ratio of the first function area, the insulation area and the second function area is about 1:1:4. The chip is fixed on the first function area and electrically connected to the first function area and the second function area, respectively, by solder wires, and the first function area and the second function area are electrically connected to a positive electrode and a negative electrode of a power source, respectively. However, the SMD holder in the prior art, during use, has a lower light transmittance after the chip is powered on.